1. Field of Invention
The invention relates to a resonant cavity device array and the method for making the same. In particular, it relates to a resonant cavity device array for wavelength division multiplexing (WDM) application and the corresponding fabricating method.
2. Related Art
As the internet and multimedia become popular, the need for a wider network bandwidth become more urgent. Optical communication technology plays an important role in future information transmissions. In particular, WDM is one of the best ways for increasing the optic fiber communication bandwidth and the transmission capacity. Several wavelengths are used on a single optic fiber. Different data signals are transmitted using the associated but distinctive wavelengths. The signals are converted by a wavelength division multiplexer into a single optical beam traveling on an optic fiber. Therefore, data signals from different sources are packed and transmitted on a single optic fiber, thereby increasing the efficiency of the bandwidth on the optic fiber.
Take a complete high-density WDM system as an example, it contains an optical transceiver module, a wavelength multiplexer/de-multiplexer, an EDFA, a wavelength extraction multiplexer, a dispersion compensator, a filter, an optical switch router, along with optical communication devices, processing circuits, and a structural optical system. However, the system with a multiple-wavelength optical transceiver module is both expensive and difficult in manufacturing. Since the vertical resonant cavity device (RCD) has the properties of being easy to change in the resonant wavelength and having a good coupling with the optic fiber, it would be a good solution to use RCD array as the optical transceiver module of the WDM system. Nevertheless, how to make several resonant cavities with different wavelengths on a single substrate is currently a problem in the field.
In the U.S. Pat. No. 6,174,749, a polycrystalline pattern is first formed on a substrate. One then controls the growth rate in different areas to form several resonant cavities, achieving the effect of multiple wavelengths. However, this method is not only difficult in controlling, the quality of the epi-layers formed on the substrate is also worse. Another example is the U.S. Pat. No. 6,117,699, which uses the selective etching method to form resonant cavities with different thicknesses before growing the distributed Bragg reflector (DBR). Afterwards, the DBR is formed through a regrowth process. Nonetheless, the depth etched using this method cannot be accurately controlled.